3.1 HIV

Question 1

What is the viral structure and behaviour of HIV

Answer 1

Genome
Capsid
Lipid envelop
Replication strategy

Question 2

What are the features of non-enveloped and enveloped virus

Answer 2

Non-enveloped virus: helical
Enveloped virus: icosahedral

Question 3

Features of HIV

Answer 3

-Retrovirus
-Infects cells with CD4
-Replicates inside cells

Question 4

How is HIV replicated in the human body

Answer 4

1. (Binding and Fusion)
   Free virus binds to CD4 molecule and a co-receptor and fuses with the cell
2. (Infection)
   Virus penetrates and empties contents into cell
3. (Reverse transcription)
   Viral RNA is converted into DNA by reverse transcriptase enzyme
4. (Integration)
   Viral DNA is combined with cell’s own DNA by the integrate enzyme
5. (Transcription)
   During cell division, protein is synthesised with the viral RNA incorporated
6. (Assembly)
   Sets of viral protein chains come together
7. (Budding) immature virus pushes out of cell with some cell membrane and breaks.
8. (Maturation)
   After immature virus breaks free of the infected cell, it is cut by the protease enzyme into individual proteins that combine to make a working virus

Question 5

How is HIV transmitted

Answer 5

1. Sexual contact
2. Transfusion
3. Contaminated needles
4. Perinatal transmission
   -transplacental
   -delivery through an infected birth canal
   -ingestion of breaks milk carrying virus

Question 6

Describe the four stages of transmission of HIV in terms of CD4 count and viral load

Answer 6

1. Seroconversion/primary infection
   CD4: high, slightly drop and increases, Viral load: very low, increases rapidly and decreases
2. Latent infection
   CD4: decreases, Viral load: increases
3. Symptomatic infection
   Pattern continues from 2.
4. Severe infection/AIDS
   Pattern continues from 2,3

Refer to graph

Question 7

Factors affecting HIV transmission

Answer 7

Type of exposure
Viral load in blood
Condom use
Breaks in skin/mucosa

Question 8

What is the Top 3 highest type of exposure in HIV transmission

Answer 8

Blood transfusion (90%-100%)
Receptive anal intercourse (1.11%)
Sharing injecting equipment (0.67%)

Question 9

List the diagnostic tests for HIV

Answer 9

Blood tests:
-serology
-PCR
-‘rapid tests’

Question 10

Aims of HIV treatment

Answer 10

Undetectable HIV viral load
Reconstitute CD4 count
Reduce systemic inflammation
Good QoL
Normalise lifespan
Reduce risk of transmission

Question 11

Why is it important to give more than 1 ARV (antiretroviral)

Answer 11

Viral replication each day
Virus mutates
Resistance to drugs develops in days
2-3 drugs makes it harder to develop resistance compared to 1 drug only

Question 12

Strategies to treat and reduce the prevalence of HIV

Answer 12

Increase condom usage
ARV treatment for prevention
Screening
Prevention of mother-to-hold transmission
Post-exposure prophylaxis (PEP)
Pre-exposure prophylaxis (PrEP)
Voluntary medical male circumcision

Question 13

What and how are ARVs used

Answer 13

NRTI +
NNRTI / Protease inhibitor/ Integrase inhibitor / CCR5 (entry) inhibitor

NRTI: Nucleoside transcriptase inhibitor
NNRTI: Non-nucleoside reverse transcriptase inhibitor

Question 14

Example of NRTI

Answer 14

Tenofovir

Question 15

Example of nNRTI

Answer 15

Doravirine

Question 16

Example of Protease inhibitor

Answer 16

Atazanavir

Question 17

Example of Integrase inhibitor

Answer 17

Raltegravir